Examples of a disk device include a magnetic disk device having a magnetic disk arranged in a case as a recording medium, a spindle motor which supports and rotates the magnetic disk, and a magnetic head which reads and writes information from and to the magnetic disk. The magnetic head includes a recording head for writing and a reading for reading.
Recently, there has been proposed a magnetic head that employs perpendicular magnetic recording and heat assist magnetic recording methods in order to increase a recording intensity and a capacity of the magnetic disk device and reduce the size thereof. The magnetic head includes a near field light generating element which generates a near field light toward a recording layer of a recording medium and a waveguide for propagating a light for generating the near field light. With this magnetic head, when writing information, a medium recording layer having a perpendicular magnetic anisotropy is locally heated by the near field light generated from the distal end of the near field light generating element, as a way to reduce the coercive force in the recording layer portion and increase the recording intensity.
In such a device, the near field light generating element and the main magnetic pole are positioned just several nanometers apart. As a result, the electric charges concentrated on the near field light generating element and the electric charges concentrated on the main magnetic pole mutually react with each other. This effect reduces the near field light intensity, and hinders the coercive force in the recording layer portion from fully decreasing. By positioning the near field light generating element and the main magnetic pole to be farther away from each other, the magnetic field intensity in the heated area of the recording medium is weakened. Therefore, the coercive force in the recording layer portion has to be further reduced by raising a laser power of a light source, so that the near field light intensity may be increased and the heating temperature of the recording layer may be raised. In such a case, however, since the heated area of the recording layer expands as a result, heat spreads in a direction of track width. As the result, information of the adjacent tracks may be degraded or erased, which limits a high recording intensity of a disk device.